Noesis is a "limited area search engine for open access, academic philosophy on the Internet." It is a dynamic project, constantly being refined, that searches for freely available, high-quality philosophy information.
PhilPapers is a directory and search engine for online philosophy articles and books by academic philosophers. The developers at Australian National University monitor journals in many areas of philosophy, as well as archives and personal pages. They also accept articles directly from users. Access to most content is free, but some journal articles may require a subscription (for which MSU users should be automatically authenticated if the Library subscribes to the journal).
PhilSci Archive is a repository of free articles and information on the Philosophy of Science. It contains over 1600 "preprint" articles with a goal to "promote communication in the field by the rapid dissemination of new work."
Philosophical blogs have flourished recently; many professional philosophers are blogging, and so are many students and amateurs. Blogs on philosophy may or may not be good sources of philosophical research, but they are a good place to stay current on a philosophical topic, discuss ideas or keep in touch on issues in the profession. Students should think twice about using blogs for research or citing them in papers, but they are a great place to explore. Here are a couple places to browse or search philosophy blogs.